Air conditioning system



July 3, 1956 J. M. SPERZEL 2,752,759

AIR CONDITIONING SYSTEM Filed May 17, 1952 r 12 65 67 62 m l0 76 INVENTOR Joseph M Sperzel BY M mi A on United States Patent AIR CONDITIONING SYSTEM Joseph Mahlon Sperzel, East Northport, N. Y., assignor to Buensod-Stacey, Incorporated, New York, N. Y., a corporation of Delaware Application May 17, 1952, Serial No. 288,407

14 Claims. (01. 62-6) This invention relates to air conditioning, and more in particular to a dual duct system for maintaining desired temperature and humidity conditions in a conditioned area. The invention relates further to a heat pump or reverse cycle heating system which supplies heat to a conditioned space or zone when heating is required and which supplies cool or dehumidified air to the space or zone as required.

In air conditioning systems it is desirable to maintain accurate control upon the temperature, supplying heated or cooled air selectively to the conditioned area or to zones thereof. Such duct air conditioning systems have beenprovided for directing separate streams of warm and cold air to the various zones of a conditioned space or area, and carefully proportioned streams of the warm and cold air are mixed at each zone to maintain the desired conditions in that zone. Such arrangements permit cooling one zone, while simultaneously heating another zone, and it has been found that such operation is desirable with suflicient frequency to make the dual duct type of installation extremely advantageous.

The present invention may be utilized with this dual duct system of operation combined with a reverse cycle heating and cooling system, whereby one stream of heated air is provided and the other stream is cooled air, both by the same refrigeration system. Hence, the cold air and the Warm air are derived from the same source, i. e., the refrigeration system. The cooling of the air is so regulated as to provide the desired dehumidification within the conditioned zones. The system also has the advantage that it may be used to do substantially nothing but cooling or substantially nothing but heating.

In the drawings, the single figure is a schematic representation of an illustrative embodiment of the invention.

At the bottom of the figure, a motor-driven compressor 2 withdraws gaseous refrigerant through a line 4 from an evaporator 5. The hot compressed gas is delivered through a line 6 to a pair of parallel condensers 8 and 9 within which the refrigerant is condensed, and the liquid refrigerant flows through a line 11 to a receiver 13. Condenser 8 is of the evaporative-cooler type enclosed in a casing 10 and having a water sprayer (not shown) and a motor-driven fan 12 which draws air into the casing through a bottom opening having air flow control dampers 14 therein. Dampers 14 are opened and closed by a control unit 16 in a manner discussed below.

Condenser 9 is positioned at the inlet end of a warm air duct 18, and evaporator is positioned at the air inlet end of a cold air duct 20, and air flows through these ducts by the action of a blower 22 driven'by a motor 24.

The liquid refrigerant flows from receiver 13 to evaporator 5 through a line 26 having an expansion valve 28 therein,

and the return line 4 has a flow-restricting valve 30 therein which is normally open but which is closed in a manner discussed below. The air flowing to ducts 18 and 20 is made up partly of a stream of recirculated or return air which is withdrawn from the conditioned area or space 2,752,759 Patented July 3, 1956 ice through a return air duct 32 and delivered to a mixing chamber 34. The remainder of the air flowing to ducts 18 and 20 is drawn in from the outside through a fresh air duct 36 having flow-control dampers 38 which are opened and closed by a control unit 40. Duct 20 has a cold-air exhaust duct 46 which has a set of normally closed dampers 48 which are operated by a control unit 50.

The general operation of the system involves the simultaneous heating of the stream of air in duct 18 and the cooling of the stream of air in duct 20, and these streams of air pass through an air distribution system to the various zones of the conditioned space or area. At each zone there is an air discharge control arrangement by which variable amounts of air from the warm air duct and the cold air duct are discharged into the zone so as to maintain the desired conditions. The air in the cold air duct is de-humidified sufliciently to give acceptable humidity conditions within each zone at all times. The system permits the simultaneous cooling of one zone and heating of another zone. Furthermore, even With maximum heating in most or all of the zones, there is cold air available to cool one or more of the zones if such action is required. Similarly during maximum cooling there is warm air available for use in any zone where that is desirable.

When the system is being used to produce substantial heating, the condenser 8 is rendered relatively ineflective by the closing of dampers 14, in which case condenser 9 will deliver substantially all of the heat to the stream of air flowing through duct 18. The heating effect is increased by circulating outside air over the evaporator 5; with such operation cold air is discharged through the exhaust duct 46 and outside air is drawn in through duct 36. However, when there is minimum heating, there is little or no warm air flowing so that there is a minimum condensing action in condenser 9, and the major portion of the condensing action is in condenser 8 with the heat being rejected from the system to the outside air. Outside air is then drawn in at 36 only at a rate to satisfy the ventilation requirements of the conditioned space.

A fully automatic control is provided which senses the need for cooling or heating, and which regulates the operation of the system to obtain the desired results. Accordingly a cold air thermostat 52 is provided which has a bulb 54 in the path of the cold air flowing in duct 20, and there is a warm air thermostat-56 which has its bulb 58 in the path of the stream of Warm air flowing in duct 18. These thermostats are the sensing elements of the control system which utilizes compressed air at an initial pressure of fifteen pounds per square inch which is supplied to each of these thermostats. The control system also includes the damper control units 16, 40 and 50 referred to above and a pair of control relays 60 and 62 each of which has a bellows 61 and a valve 65 controlled thereby through a lever 63. In addition to the above, the control system has a refrigerant-pressure relay 64 which has a bellows 71 which controls a valve 69.

Relay 64 has its bellows 71 connected through a refrigerant pressure line 66 to the receiver 13, and this bellows moves valve 69 downwardly from the position shown to permit air to flow from a line 68, to a line 70 when the receiver pressure is below certain predetermined air as sensed by bulb 58'. A similar line 72 is connected tothe cold air thermostat 52, and air is supplied to this line at a pressure which'is varied in accordance with the temperature of the cold air as sensed by bulb. 54. Line 68 also extends to the bellows 61 of relay 60, and line 72 extends to the valves 65 of both of relays 60 and 62, and it also extends to the flow-restricting valve 30 which is in the intake line to the compressor. Line 70 extends from the valve 69 and relay 64 to the bellows 61 of relay 62. A line 74 extends from relay 62 to control unit 16, and a line 76 extends from relay 60 to control units 50 and 40. The linkage of the set of dampers 38 is provided with a minimum opening stop (not shown) so that the dampers have a minimum opening sutlicient to supply the ventilation requirements.

Thermostats 52 and 56 are adapted to maintain controlled air pressures in their respective lines 72 and 68. Each thermostat throttles the air as it fiows into its line so as to vary the pressure in the line in accordance with the temperature as sensed by the thermostat bulb. The

details of the adjustment and the operation are to some extent illustrative, but they represent an example of working characteristics of the illustrative embodiment. The system is so constructed as to allow for the temperature of the air in the cooled air duct to vary from 50 F. down to 40 F., and the air pressure in line 72 is varied between three pounds per square inch at 50 F. or above to thirteen pounds per square inch at 40 F. or below. Within the range between these two temperatures, the change in air pressure is at the rate of one pound for each degree of temperature change. Similarly thermostat 56 varies the air pressure in its line 68 between three pounds at 90 F. or above and thirteen pounds at 80 F. or below, and the rate of change is one pound per degree change in temperature. In each instance the minimum pressure is at the maximum temperature and the maximum pressure is at the minimum temperature. As indicated above, relays 60 and 62 are identical and each has a flow throttling arrangement illustratively formed by the valve 65 at the top by which the air How is throttled to an outlet pressure which is varied in accordance with the pressure exerted in the bellows61 at the bottom of the relay. Similarly relay 64 has a flow throttling arrangement formed by valve 69 at the top by which the air flow is throttled in accordance with the refrigerant pressure exerted in the bellows 71 from the receiver through line 66. Relay 64 has a reverse action so that a drop in the receiver pressure (and condensing temperature) opens valve 69 and causes relay 64 to tend to maintain a higher air pressure in line 70. However the pressure in line 70 is produced by a flow from line 68 through control relay 64, and therefore a drop in the receiver pressure merely changes the setting of the relay 64 and does not change the pressure in line 70 unless the pressure in line 68 is at the higher value. In a similar manner, the'rise in pressures in lines 68 and70 causes valve 65 to open and this increases the settings of relays 6t} and 62; and when there is a high pressure in line 72 this is transmitted through relay 60 to line 76 and through relay 62 to line 74.

Flow control dampers 14 are normally open and are closed gradually as the pressure in line 74 is increased from five pounds to ten pounds. Dampers 48 are normally closed and are gradually opened when the pressure in line 76 is increased from eight to thirteen pounds. When no heating is called for, dampers 38 are maintained in a partially open position to give the desired fresh" or outside air intake. When substantial heating is required, unit 40 is operated gradually to open the dampers completely; this opening is eifected by a rise in pressure in line 76 from eight to thirteen pounds. Valve 30 is normally open, but it is closed gradually to maintain the temperature of evaporator high enough to avoid the formation of ice thereon. Hence, valve starts to close when the pressure in line 72 rises above three pounds and the valve is closed (i. e., at its minimum opening position) when this pressure reaches thirteen pounds. Valve 30 then provides the minimum passageway for refrigerant to maintain the minimum cooling eflect. The controls and electrical circuits for the compressor motor and for the two fan motors have been omitted from the drawings, and these and other electrical control facilities are of standard construction.

With the above arrangement the system operates automatically and changes gradually from a condition where the load is primarily cooling to a condition where the load is primarily heating. At the time that the load involves a fair demand for cooling, the thermostat 52 maintains an air pressure of eight pounds in line 72 when the cold air temperature is 45 F. Assuming that conditions are such that the warm air temperature is F. at that time, the pressure in line 68 is also eight pounds. At this time the pressure in the receiver is normally sufficiently high to maintain relay 64 restricted and the pressure in line 70 is held to five pounds. Therefore relay 62 holds the pressure in 74 to five pounds, even though the pressure in line 72 is eight pounds. Valve 30 is partially closed by the eight pound pressure in line 72.

With the conditions just stated, a rise in the temperature of the cold air reduces the pressure in line 72 to a minimum of three pounds at 50 F. or higher. This reduced pressure in line 72 causes valve 30 to reopen. If there is a rise in the temperature of the warm air, the air pressure in line 68 is reduced and this has no effect. However, if the cold air remains at 45 F. and the warm air remains at 85 F. and the condenser temperature and receiver pressure fall, the relay 64 opens so as to increase the pressure in line 70; this efiects relay 62 so as to raise the pressure in line 74, and dampers 14 are moved toward the closed position an amount depending upon the rise in pressure. The partial closing of dampers 14 tends to reduce the refrigerant condensing action in condenser 8 and this tends to raise the pressure in the condensers and the receiver. Thus with the operating conditions as specified above, there is a tendency for the system to maintain a somewhat stable balance throughout the system.

Assuming with the above-stated conditions that there is a drop in the temperature of the cold air which would indicate a reduction in the cooling load, the thermostat 52 would increase the air pressure in line 72. This would further close valve 30 and would make the higher pressure air available to relay 62. If there is a simultaneous drop in the warm air temperature, the pressure in line 68 would also be increased, and these increases in pressure,

would be transmitted through relay 60 to line 76. Furthermore, the receiver pressure would be apt to drop so as to permit the higher pressure to be exerted in line 70 and through relay 62 to line 74. The increased pressure in line 74 would act through control unit 16 to close dampers 14 as has been discussed above.

The movement of dampers 14 to their fully closed position stops the flow of air so that condenser 8 is rendered relatively inefiective. This causes an increase in the condenser pressure so that the air passing over condenser 9 is heated more and this condenser delivers substantially all of the heat of condensation to the screen of warm air. Thus the temperature of the warm air is elevated again. With this condition of operation the system is prepared to handle an appreciable heating load or it may handle an appreciable cooling load in some zones and appreciable heating loads in other zones.

With the conditions just discussed, it has been assumed that the pressures in lines 68 and 72 have been at eight pounds initially, but that the temperatures of the cold air and the warm air have dropped, and that the pressures in lines 68 and 72 have risen above eight pounds. The rises in these two pressures are transmitted through relay 60 to line 76 with the pressure in line 76 being the lesser of the pressures in lines 68 and 72. It has been indicated above that a rise in pressure in line 76 above eight pounds acts through control unit 50 to gradually open dampers 48, and it also acts through control unit 40 to tend to open dampers 38. Thus the excessive cold air from conduit 20 is discharged through exhaust duct 46 and replacement outside .air is drawn in through fresh air duct 36. With dampers 48 and 38 fully open, a very substantial air fiow is produced over evaporator'S which cools the air and extracts heat therefrom; and this heat is delivered through condenser 9 to the stream of warm air in duct 18. Mixing of this fresh air with the recirculated air in chamber 34 is not objectionable because this insures a proper supply of fresh air to the conditioned space. Furthermore, the re-circulated air which is dischar ed has been passed over the evaporator and thoroughly cooled so that the heat is extracted from it. Thus a high degree of efliciency of operation is maintained with all conditions of operation.

It should be noted that the invention is adaptable to a wide variety of systems and that it overcomes difliculties and solves problems which have been involved with arrangements in the past to accomplish similar purposes. The dual duct system may be for high or low pressure air and under some circumstances secondary heat exchange equipment may be used to cool or heat the air in the ducts. The humidity is maintained Within very satisfactory limits even under extreme operating conditions, and the system operates without the loss of efficiency through wide variations in the internal cooling loads and wide variations in outside temperatures and hurnidities.

It has been noted that the condenser 8 dissipates heat to the air at a substantial rate as is required to maintain optimum conditions in the system. Furthermore evaporator 5 absorbs heat from outside air which is here advantageously drawn into the cold air duct and then discharged through the exhaust duct 46. One important aspect of the invention is that a simplified and efiicient system is provided which integrates the total heating and cooling loads and which handles each of these loads fully automatically. When the system is of the dual duct type, as in the illustrative embodiment, the cold air and warm air are mixed or blended at the various zones of the conditioned space. Certain aspects of the invention are quite applicable to systems where all or part of the blending or mixing of the warm and cold air occurs centrally, that is, adjacent the conditioning apparatus. Regardless of the type of air distribution, the system contemplates the cooling and heating of air to take care of varying heating and cooling loads, or one load may be substantially constant. An increase in the rate of flow of either cool or warm air generally causes an increase in the cooling or heating, as the case may be, without undue delay and without excessive cooling or heating of either stream. Likewise there is stability of action when one or both of the loads decreases.

The control system of the illustrative embodiment of the invention utilizes compressed air and this has advantages in this particular arrangement. However, the invention contemplates that electric control may be provided for all or part of the system. Other modifications and changes can be made within the scope of the invention as set forth in the claims which follow.

I claim:

1. In an air conditioning system, the combination of, a dual duct air distribution system for supplying separate streams of warm and cold air to the conditioned space, a refrigeration system including a condenser to heat air to provide the stream of warm air and an evaporator to cool air to provide the stream of cold air and also having an auxiliary condenser to dissipate excess heat, and an automatically operating control system to maintain predetermined temperature conditions for the warm and cold air and to control the operation of said refrigeration system and the dissipation of heat by said auxiliary condenser including means responsive to predetermined low temperatures of the streams of cold air and warm air to restrict the dissipation of heat by said auxiliary condenser.

2. A system as described in claim 1 which includes, means to discharge cold air from the cold air duct, and control means to cause cold air to be discharged when the cold air temperature is at or below a predetermined level and the warm air temperature is belowa predeter means to draw air from the conditioned space and to mix it with fresh air and to supply it to said duct system, and means to restrict the entry of fresh air when either the cold air temperature is not satisfied or the warm air temperature is satisfied.

4.. A system as described in claim 3 wherein said refrigeration system includes a compressor to which refrigerant flows from said evaporator, and means to restrict the flow of refrigerant to the compressor when the cold air temperature is below a predetermined value.

5. A system as described in claim 4 wherein the control is accomplished by air under pressure and the system includes thermostat air pressure controllers responsive respective to the temperatures of the warm and cold air, and a control unit responsive to the pressure of the condensed refrigerant to prevent the reduction in the dissipation of heat by said auxiliary condenser when the pressure of the condenser refrigerant is above a predetermined value.

6. A system as described in claim 5 wherein said auxiliary condenser is of the air cooled type and includes a casing construction and fan means to promote flow of air therethrough and damper means to stop such flow, and wherein said condensers are connected in parallel to receive compressed refrigerant gas and to discharge liquid refrigerant to receiver means.

7. A system as described in claim 6 wherein said control system includes air pressure relay units upon which control pressure from said thermostats is exerted with a gradually changing control effect.

8. In an air conditioning system, the combination of, means to pass air through a heating zone and a cooling zone, a refrigeration system having heat exchange facilities for heating the air in said heating zone and cooling the air in said cooling zone, means to promote the dissipation of heat from the system to the outside air, means to provide absorption of heat by the system from the outside air, and control means to exert control influences upon the system toward maintaining the temperature of the air leaving said heating zone within a predetermined range and to maintain the temperature of the air leaving said cooling zone within a predetermined range with a throttling control effect.

9. In an air conditioning system, the combination of, means to cool a first stream of air, means to heat a second stream of air, means responsive to the temperatures of the two streams of air being below predetermined values to discharge a portion of the first stream of air and to increase the heating of the second stream of air.

10. A system as described in claim 9 which includes,

' means responsive to the rise in the temperatures in the two streams of air above predetermined values to increase the cooling effect upon the respective streams of air and to decrease the heating effect.

11. A system as described in claim 10 wherein said means to heat and said means to cool are components of a refrigeration system which includes, means responsive to the conditions of gas condensing to prevent the increase in heating when the pressure of the gas condensing is above a predetermined value.

12. In an air conditioning system, the combination of, a dual duct air distribution system for supplying separate streams of warm and cold air to different zones in the conditioned space, a refrigeration system of the compression type having its condenser arranged to heat the air entering the warm air duct and its evaporator arranged to cool the air entering the cold air duct, a single blower to direct air through said dual duct system from an air mixing zone, means to return air from the conditioned space to said air mixing zone, air intake means for fresh air to pass into said mixing zone, cold air exhaust means which is operative to discharge cold air when the temperature thereof drops below a predetermined value, and means to promote the dissipation of condenser heat to the outside air when the temperatures in the two ducts rise above predetermined values.

13. In an air conditioning system, the combination of, a refrigeration system which is adapted to heat air in a warm air chamber and an evaporator arranged to cool air in a cold air chamber, blower means to direct air through said chambers, distribution means to deliver air from said chambers to a space to be conditioned to maintain predetermined conditions Within the space, air exhaust means to exhaust air to the outside when the air within said cold air chamber is below a predetermined value, and means to dissipate heat from said refrigeration system to the outside when the temperatures of the air within said chambers rise above predetermined respective values.

14. In an air conditioning system, the combination of,

a dual duct air distribution system for supplying separate streams of warm and cold air to the conditioned space, a refrigeration system of the compression type which has an evaporator and a condenser, means forming a mixing zone, air intake means for fresh air to pass into said mixing zone, means including said condenser to heat a stream of air flowing from said mixing chamber and thence through the warm-air duct, means including said evaporator to cool a stream of air flowing from said mixing chamber to the cold-air duet, cold air exhaust means which is operative to discharge cold air when the temperature thereof drops below a predetermined value, air circulating means to circulate air from said mixing chamher along the respective heating and cooling paths, and thence through said ducts, and means to promote the dissipation of condenser heat to the outside air when the demand for warm air from said warm-air duct is insutficient to dissipate all of the condenser heat.

References Cited in the file of this patent UNITED STATES PATENTS 1,751,806 Fleisher Mar. 25, 1930 1,837,798 Shipley Dec. 22, 1931 2,097,539 Tomlinson Nov. 2, 1937 2,172,877 Parcaro Sept. 12, 1939 2,268,769 Newton Jan. 6, 1942 2,619,802 Kline Dec. 2, 1952 

